The present invention generally relates to cutting tools and methods for cutting materials used on or in houses and other structures. More particularly, the invention is directed toward fiber-cement cutting tools and methods for cutting fiber-cement composite materials.
The exterior surfaces of houses and other structures are often protected by exterior siding products made from wood, vinyl, aluminum, bricks, stucco, fiber-cement and other materials. Wood and fiber-cement siding (FCS) products, for example, are generally planks, panels or shakes that are xe2x80x9chungxe2x80x9d on plywood or composite walls. Although wood siding products are popular, wood siding can become unsightly or even defective because it may rot, warp or crack. Wood siding products are also highly flammable and subject to insect damage. Therefore, wood siding products have several drawbacks.
FCS products offer several advantages compared to other types of siding materials. FCS is generally a composite material composed of cement, silica sand, cellulose and binders. To form FCS panels and planks, a liquid fiber-cement composite is rolled or pressed into the shape of the planks or panels, and then the fiber-cement composite is cured. FCS is advantageous because it is nonflammable, weatherproof, and relatively inexpensive to manufacture. Moreover, FCS does not rot and insects do not consume the fiber-cement composites.
FCS products are typically installed by a siding contractor at a particular job site or a modular home manufacturer in a factory. To install FCS planks, for example, the planks are cut to a desired length and then nailed to plywood or wood-composite panels in a manner similar to hanging planks of cedar siding. After the FCS is installed, trim materials are generally attached to the structure. The FCS and the trim materials are subsequently painted.
FCS is often cut using an abrasive disk in a manner similar to cutting wood products with a hand-held power saw or a table saw. Cutting FCS with an abrasive disk, however, generates a very fine dust that creates an unpleasant working environment. The fiber-cement composite materials are also highly abrasive, and thus the abrasive-disks may wear out quickly. Thus, there are many disadvantages to cutting FCS with an abrasive disk.
FCS may also be cut with shears having opposing blades or hand-held cutting tools having a reciprocating cutting blade. Pacific International Tool and Shear, Ltd. has developed several shears and hand-held cutting tools, including those set forth in U.S. Pat. Nos. 5,570,678 and 5,722,386 (the xe2x80x9cPacific Patentsxe2x80x9d), and U.S. patent application Ser. No. 09/036,249, all of which are herein incorporated by reference. Several embodiments of the shears disclosed in the Pacific Patents have an actuator, an upper blade assembly coupled to the actuator to move along a cutting path, and a lower blade assembly positioned under the upper blade assembly. The upper blade assembly has an upper blade, and the lower blade assembly has a lower blade. The shears disclosed in the Pacific Patents can also have first and second support members on either side of the lower blade, and the first and second support members can have first and second support surfaces in a common workpiece support plane. The lower blade in the Pacific Patents is configured such that its cutting edge is either at the support plane or projects slightly above the support plane toward the upper blade. In operation, a workpiece slides across the lower blade until a desired cutting plane is aligned with the upper and lower blades. The actuator then drives the upper blade against an upper surface of the FCS workpiece to penetrate the upper and lower blades into opposite sides of the workpiece. The upper and lower blades generate a crack that propagates along the cutting plane through the workpiece to cut the workpiece along the cutting plane.
Although the shears disclosed in Pacific Patents cut a clean edge in FCS without producing dust, one operating concern of these shears is that it can be difficult to cut long sections of an FCS workpiece in a single stroke of the blades. For example, to cross-cut a 4xe2x80x2xc3x978xe2x80x2 panel of xc2xc-inch thick FCS, Pacific International Tool and Shear developed a shear similar to those described in U.S. Pat. No. 5,570,678 that required three pneumatic cylinders operating at a pressure of 150 psi. The same shear, however could not cross-cut a 4xe2x80x2xc3x978xe2x80x2 panel of {fraction (5/16)}-inch thick FCS operating at a pressure of 150 psi in each pneumatic cylinder. One solution to this problem is to use more force to drive the upper and lower blades into the FCS workpiece, but this solution requires larger and/or more actuators that significantly increases the cost and the number of moving components that can malfunction.
Another operating concern of the cutting tools disclosed in the Pacific Patents is that the upper and lower blades may wear relatively quickly. FCS quickly grinds or otherwise abrades most metals because it is highly abrasive. As a result, any contact with FCS dulls the cutting edges of the upper and lower cutting blades. The lower blades of the shears disclosed in the Pacific Patents are particularly susceptible to wear because the FCS workpiece typically slides across the edge of the lower blade to position a cutting line on the workpiece between the upper and lower blades. Thus, even though the shears disclosed in the Pacific Patents work well in many applications, there is a need to efficiently cut long sections of FCS and reduce wear of the cutting blades.
The present invention is directed toward devices and methods for cutting fiber-cement materials, such as siding or other materials. A fiber-cement siding cutting tool in accordance with one embodiment of the invention includes an actuator having a driver that moves along a stroke path between a release position and a cutting position. The fiber-cement siding cutting tool can also have a pair of cutting blades including a first cutting blade having a first cutting edge and a second cutting blade having a second edge. The first cutting blade is coupled to the driver to move along the stroke path between the release position and the cutting position. The second cutting blade can be positioned along the stroke path such that the first cutting edge faces the second cutting edge. The first cutting blade, for example, can be superimposed over the second cutting blade.
The fiber-cement siding cutting machine can also include a workpiece support assembly having a first support member on a first side of the stroke path and a second support member on a second side of the stroke path. The first and second support members are spaced apart from one another by a support distance, and each of the first and second support members has a support region to support a fiber-cement siding workpiece in a support plane. The support regions, for example, can be spaced apart from the second cutting edge toward the first cutting edge in the direction of the stroke path by a bending distance such that the support plane is spaced apart from the second cutting edge by the bending distance. The support members accordingly space a tensile side of the workpiece apart from the second cutting edge by the bending distance.
The first and second support members can have several different embodiments that position the tensile side of the workpiece away from the second cutting edge. In one embodiment, for example, the first and second support members are first and second elongated rollers that rotate about first and second rotational axes, respectively. The first and second elongated rollers can extend at least substantially parallel to a lengthwise dimension of the second cutting blade such that the support regions are defined by the uppermost points of the first and second rollers. The first and second support members can alternatively be first and second wheels or elongated bars that are spaced apart from the second cutting edge by the bending distance.
In one embodiment of a method for operating the FCS cutting tool, the actuator initially holds the driver in the release position as an FCS workpiece moves over the first and second support members until a cutting plane in the workpiece is aligned with the stroke path. The FCS workpiece accordingly has a first side facing the first blade and a second side facing the second blade. Because the first and second support members space the FCS workpiece apart from the second cutting edge when the driver is in the release position, the second cutting blade does not engage the second side of the FCS workpiece at this point of the method. The actuator then moves the driver along the stroke path to drive the first cutting edge against the first side of the FCS workpiece. The first cutting blade accordingly exerts a force that bends the FCS workpiece between the support members to impart compressive stress to the first side of the FCS workpiece and tensile stress to the second side of the FCS workpiece. As the driver continues to move along the stroke path, the FCS workpieces continue to bend until the second side of the workpiece engages the second cutting edge. The first and second edges then penetrate into the first and second sides of the workpiece to generate a crack that propagates along the cutting plane through the workpiece.